Remove bottom-up CPU profile

Bottom-up view of CPU profile can be restored based on top-down profile data. So there is no need to spend resources on creating both of them inside V8.

BUG=None

Review URL: https://codereview.chromium.org/12825003

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@13958 ce2b1a6d-e550-0410-aec6-3dcde31c8c00